The present invention relates generally to the art of infrared-reflecting coated glass products, and more particularly to non-iridescent, high transmittance, low emissivity, infrared-reflecting coated glass products.
Transparent infrared-reflecting films such as tin oxide may be deposited on a substrate such as glass by a variety of methods, including the application of thermally decomposable compounds to a heated surface. Useful methods for forming transparent infrared-reflecting tin oxide films are taught in U.S. Pat. No. 3,107,177 to Saunders et al, U.S. Pat. No. 3,677,814 to Gillery, and U.S. Pat. No. 4,263,335 to Wagner et al.
Tin oxide films are especially effective infrared reflectors at thicknesses of about 1000 to 8000 Angstroms. However, at such thicknesses the films tend to display interference effects, i.e., multiple visible colors commonly referred to as iridescence. These interference effects render the coated glass aesthetically unacceptable for most architectural applications. Iridescence is not observed in thinner films; however, these films have insufficient infrared reflectance to be practically useful. Likewise, iridescence is not observed in thicker films; however, these films tend to be hazy and difficult to deposit uniformly. Therefore, various methods to mask interference effects have been developed.
U.S. Pat. No. 3,710,074 to Stewart discloses an electrically heated multiple glazed window unit having an electroconductive coating on an enclosed surface and a selective reflecting film having an absolute infrared reflectance of at least 0.7 to improve the heat insulating character of the unit and reduce the visible iridescence of the conductive film.
U.S. Pat. No. 4,069,630 to Chess et al discloses a heat reflecting multiple glazed window comprising a colored, heat absorbing exterior glass sheet having a heat reflecting tin oxide film on its interior surface, and an interior glass sheet which may be either clear glass or colored. The tin oxide film typically has an interference color from first order red to fourth order red, the visual effect of which is attenuated by the colored heat absorbing glass.
U.S. Pat. Nos. 4,187,336; 4,206,252 and 4,308,316 to Gordon disclose transparent glass window structures comprising a glass sheet bearing a first coating of infrared reflective material, wherein the observance of iridescence resulting from the first coating is reduced by a second coating of particular refractive index and thickness providing at least two interfaces forming means to reflect and refract light to interfere with the observance of iridescence.
U.S. Pat. No. 4,377,613 to Gordon discloses transparent window structures comprising a glass sheet bearing a coating of infrared reflective material wherein the observance of iridescence is reduced by provision of a very thin coating system beneath the infrared reflective coating which reflects and refracts light to interfere with the observation of iridescence.
U.S. application Ser. No. 768,922 filed Aug. 23, 1985, by V. A. Henery et al discloses an alternative method for masking the visible interference effects of an infrared reflecting film in a window unit, which involves masking e visible interference effects of an infrared reflecting film by means of a second film having a uniform reflectance in the visible wavelength range combined with a luminous reflectance which is significantly higher than that of the infrared reflecting film. To produce a high transmittance, low emissivity unit, the thickness of the infrared reflecting film is preferably chosen to correspond with the first minimum in the reflectance curve.